Field-coil insulation and process of forming same.



N0- 830,419. PATENTED SEPT. 4, 1906. L. W. DOWNES.

FIELD COIL INSULATION AND PROCESS OF'FORMING SAME.

APPLIOATION FILED OO'I.2Z, 1904.

3 SHEETS-SHBET l.

.No. 830,419. PATENTED SEPT. 4, 1906. L. W. DOWNES.

FIELD COIL INSULATION AND PROCESS OF FORMING SAME.

3 SHEETS-SHEET 2.

Witvwwm PATENTED SEPT. 4, 1906.

L. W. DOWNES.

FIELD COIL INSULATION AND PROCESS OF FORMING SAME.

APPLICATION FILED 0GT.Z2, 1904.

3 SHEETS-SHEET 3.

LOSiS N. DOWNES, OF PROVIDENCE, RHODE ISLAND.

FIELD-COIL INSULATION AND PROCESS OF FORMING SAME.

Specification of Letters Patent.

Patented Sept. 4, 1906.

Anplication filed October 22. 1904. Serial No 229,626.

To all whom it may concern:

Be it known that I, LoUIs W. DOWNES, a resident of Providence, Rhode Island, have invented a new and useful Improvement in Field-Coil Insulation and Processes of Forming the Same, which invention is fully set forth in the following specification.

This invention relates to the construction of electromagnetic coils for electric motors and d amos, and particularly to the insulation t ereof and the process of forming said insulation.

One of the most important desiderata in the use of any magnet-Wire is to prevent contact of the convolutions with water or moisture. Railway field-coils, it is well known, are frequently subjected to partial immersion in water for quite lengthy periods, this undesirable condition being greatly aggravated by the frequent presence in the water of large percentages of salt or brine. As the Water is quickly heated by the heat developed in the motor it results that the coil is sometimes subjected for many hours to the destructive action of a hot briny solution, one of the worst conditions that could be brought about. It will be readily appreciated that no matter how great the heat-resisting properties of the wire trouble will occur, due to the gradual carbonization of the materials ordinarily used in constructing the insulating Wrapping or covering of the coils. This outer covering gradually hardens and becomes crisp and brittle by the action of the heat developed in the coil. Being at the same time subjected to severe vibrations and jars, cracks ultimately develop and admit water to contact with the convolutons, causing the coil to quickly break down.

4 My principal object is to prolong the life of electromagnetic coils, particularly field-coils used on electric cars or in other locations where they are of necessity exposed at times to water or moisture by the production of an insulation which will withstand unusual temperatures and not be readily affected by water or moisture. ,Practical use and extensive experiments have demonstrated that coverings of fabric made of cotton and similar vegetable fibers are not sufficiently heat-resistant and are quickly destro ed under the conditions referred to. The igh heat-resisting roperties of asbestos are ver favorable to its use for the purpose. On t e other hand, its hygroscopic properties are unfavorable.

I propose, however, to employ as the principal part of my improved insulation asbestos so treated as to render it water-repellent. Extensive experiments have demonstrated that no varnish, oil, japan, or other water- .proofi'n com ound containing a vegetable or oxidiza le oi can be used as to that portion of the insulation next to the convolutions of the coil, for the reason that such materials or oils readily decompose, producing active acids which invariably break down the insulation resistance by the'formation of copper salts. So far as I am aware the only materials that can be safely used for waterproofing that portion of the asbestos covering which is directly over the convolutions of wire are those made from the paraffin conipounds. There are a number of such con'1 positions of excellent quality on the market under various trade names; but as drying oils and compositions having a drying-oil base, such as japans, possess very desirable proper-- ties and considerable resistance to heat when dry I find. it very advantageous to use such water-proofing materials at an outer portion of the insulating-covering where they are effectivel isolated from all possibility of cont. ct Wit 1 the copper. IVhen so used,thedrying oil or composition thereof prevents the paraffin compound within from escaping when melted by the heat of the coil and also prevents the admission of water or moisture from without. In the preferred form, therefore, myimproved insulation comprises a first covering of asbestos applied over the convolutions of the coil and then saturated or impregnated with a non-oxidizable substance, referably of the paraffin variety, and a secon covering, preferably of asbestos, to which latter is applied a waterproofing compo tion capable of withstanding high tempera ..e, such as a drying-oil or composition thereof. The insu ating-casing and the completed coil also possess other important characteristics, and the invention also embraces improvements in the process of forming and applying the insulation, all of which will be fully understood by reference to the acconi ying drawings, wherein the invention is ilrated with reference to a field-coil.

Figure 1 shows a coil of field-coil with the terminals t ed in place. Figs-2 and 3 illustrate the peferred manner of applying a layer of asbestos formed of pieces of asbestos paper over the coil. Fig.

suitable for a the coverings of 4 illustrates the preferred way of applying another layer of asbestos over the first la er. Fig. 5 illustrates the shape of the various pieces of asbestos paper employed in forming igs. 2, '3, and 4. Fi 6 shows the coil after the outer winding 0 'asbestos braid has been ap lied thereto. Fig. 7 shows pieces of asbestos raid sewed together so as to be suitable for use in covering of the corners of the coil. Fig. 8 is a plan view, and Fig. 9 a side view, of an im roved form of terminal, and Fig. 10 com rises detail views of parts of the terminal. ig. 1 1 is a transverse sectional view through the insulating-covering, showing the arrangement of theparts of the terminal with relation to said insulation. Fig. 12 is a perspective view of a form, partly broken away to show a covering ap lied thereto. Fig. 13 is a sectional view, an Fig. 14 a lan, partly in section, showing how the tra 'ke parts of the insulation fit together; n Fig. 15 is a perspective view of one of the tra -.li e parts.

11 referring herein to the employment of asbestos paper, I intend to embrace asbestop in any sultable sheet form, thou' h I prefer to employ, on account of its 0 eapness and adaptibility to the urposes of this invention,what is commercia ly known as asbestos tos paper. I may also employ an asbestos composition in plastic form, the same being spread out upon the coil or a form and allowed to set. In practice I have obtained the best results by employing in forming the coil wire insulated with asbestos in accordance with the inventions of my Patents No. 534,785, of February 26, 1895, and No. 709,001, of September 16, 1902, and commercially known as deltabeston wire.

The rocess of insulating a coil as illustrated in Figs. 1 to 11 is as follows: Wrappings of asbestos paper 15 and 16 are applied to opposite sides of the wire-coil beneat the bare ends 17 and 18 of the wire. Thin sheets of micanite 19 and 20 are a plied over the Wrap ings of asbestos 15 an 16. The termina s 21 and 22 (of a preferred construction hereinafter described) are then applied over the micanite sheets, and the bare ends 17 and 1-8 of the wire are soldered to the terminals in the usual way. Wrappings of stout asbestos twine 23, 24, 25, and 26, extendin over the wire ends 17 and 18, are next app 'ed to securely bind the terminals to the coil. The coil is now ready for the formation thereabout of the first jacket, made up of pieces of asbestos paper, the latter being preferably dampened with a thin solution of flour paste or any good wall-paper aste, the dampening being sufficient to ena Ie the paper to be readily shaped to the form of the coil. Care should be taken that the solution is not so strong as to glaze over the paper, and thereb prevent the latter from becoming saturate with the water-repellent compound-applied later. To

of asbestos paper.

facilitate the application of the asbestos pa= per, we have found it ex edient to cut it into various shapes, enabling it to be readily formed to the irregular surface and curved corners of the coil, the pieces being so disposed as to frequently break joints, thereby preventing openings or imperfections in the shell at points where the pieces of paper meet. In

ig. 5 I have illustrated pieces of asbestos paper cut to a form suitable for use in connection with a standard General Electric No. 52 motor field-coil. These pieces can be properly marked or identified, so that the workman will know exactly what piece is to be used in each position. As herein described, the first jacket is composed of four superposed layers A greater or less number of layers may be used. In fitting the different pieces to the coil I prefer to appl to the paper with a suitable brush an abun ance of aste, preferably of an approximate density of i ive degrees as measured on an ammonia hydrometer. Ipreferably em 10 paper about one one-hundredth of an inc t 'ck, and it is expedient to lay the paper flat on a board or in a shallow pan in applying the paste, so that the latter will thoroughly impregnate and wet the paper. In this condition the paper may be readily a plied without the formation of creases. eferring to Fig. 2, the first layer of asbestos paper may be applied by wrapping the piece coil after being thoroughly saturated with the liquid paste, care being taken to stretch the pziper tightly about the coil. Then pieces B an C0 are wrapped about the coil in the positions indicated, the lap of the two piecesC Obein carefully ressed down to ive a perfectly-tig t joint: he four sides 0 the coil now being covered the cornerieces D (sixteen in all, eight on the up er si e of the coil and eight on the lower side thereof) are now ap lied and tightly ressed down by hand. ieces D are slight y la ped at their ed es, as clearly illustrated. T e four inside en pieces E and the four outside end ieces F are now placed in position and tightly pressed down by hand. This completes the first layer, the pieces composing the same overlapping each other at the joints. While the first layer is still damp with the paste applied thereto in building it up om the different pieces of paper, I proceed to apply the second layer. (Illustrated in Fig. 4.) The two pieces G, Fig. 5, are first laid alon the inside of the coil. The pieces H H our in all) and the pieces I I (four in all) are next applied to opposite sides of the coil. Finally the two ieces J J are applied about the perimeter o the coil, care aving been taken to press all of the pieces down by hand, so that they closely conform to the sha e of the coil and to lap the joints, so as to orm a second continuous layer of asbestos paper. A third layer, simiabout the end of the lar to that of Fig. 2, and a fourth layer, similar to that of F1 4, are now preferablglapplied, the result eing a jacket of four t 'c nesses of asbestos paper completely incasing the wire-coil and closely conforming to the shape thereof. In applying the pieces of asbestos paper openings or notches may be cut therein to closely fit about the stems of the projecting terminals. The coil is next thoroughly dried out the dryin bein preferably slowly effected in air, so t at t e moisture from the inside may have ample opportunity to esca e. After standing over night the coil wil have the appearance of being quite dry; but I have discovered that it will still contain considerable moisture. To completely remove all moisture, it is desirable to place the coil in an oven and leave it there or a suflicient timesay for a period of two a or three hours to raise the tern 'erature of the whole mass to about 300 ahrenheit. U on removin the coil from the oven and w ile it is still hot it is completely immersed in a paraflin insulatin com osition of the kind now generally used for t iis urpose and allowed to remain therein until the coil is thoroughly cooled. It is desirable to keep this paraffin composition fairly thin by the addition of na htna from time to time, as the heat of the COll tends to volatilize the naphtha which is used as a solvent for the parafiin composition. When no bubbles appear at the surface of the paraflin composition and after the coil has become quite cool, the latter is removed frointhe bath and allowed to dry out. It will readily dry in a few hours. The process up to this point results in a coil completely and tightly incased in a covering or jacket 52, of asbestos paper rendered waterproof by impregnation with a non-oxidizable waterproofing materiala paraffin com osition. A secondjacket 55 is now applie over the first jacket, the same being composed principally of four layers of asbestos paper built up in the same manner as the layers of the first jacket. After bein allowed to air-dry these layers will be read to receive an outer wrapping, preferably of asbestos tape 27, Fig. 6, of a thickness of about three one-hundredths of an inch, which may be said to form part of the outer jacket. This asbestos tape can be procured on the market in suitable width, referably about three-fourths of an inch. he coil should be tightly wrapped with a complete layer of asbestos tape, care being taken to wind the corners so as not to make them bulky. A preferred method of applying tape at the corners is illustrated in Figs. 6 and 7. Fig. 7 shows four pieces of tape sewed together with asbestos twine 29, the sewing being of a length just sullicient to extend across the outer edge of the coil. In applying these pieces to the bend of the coil the loose ends 30 of the several pieces are caused to lap each other, as shown in Fig. 6, and are bound in place by the regular wrapping of the sides. After completing the wrapping the comerpieces should be sewed to t e side wrapping at the points 31 32, the result being an outer wrap ing of tape strong quite even, and free from unches. ,The coil is now placed in an oven and ra idlyraised to a temperature of about 300 ahrenheit, which temperature is maintained for a period of one hour, and while still hot the coil is removed from the oven and immersed in a bath of good baking-j apan or similar dryin -oil composition or drymgoil alone, in whic it is allowed to remain until the jacket 55 and its wrapping of ta e are thoroughly'saturated. Upon remova from the japan the coil is allowed to drain for an hour or two to remove excess of the composition and is then placed in a baking-oven and baked for a eriod of three or four hours until quite bar at a temperature of from 300 to 350 Fahrenheit. Upon removal from the oven and while still hot I preferably again place it in the japan-bath in order to complete the saturation, after which another draining and another baking at the temperature specified will com lete the coil. It will be appreciated that t e drying-oil composition or japan with which the outer jacket is impregnated is excluded from 'possible contact with the wire by the inner jacket.

It will be found that with very little experience coils can be insulated in the manner above described at comparatively low cost and that the insulation is practically indestructible by heat and moisture. Experience has demonstrated that field-coils so insulated may be kept in perfect condition by removal at the most, say, twice a year for a dipping in japan followed by baking.

One of the chief sources of trouble in the use of field-coils is due to the admission of water or moisture to the inside of the coil at the point where the terminals pass through the outer insulation, especially when one terminal is located at the bottom of the motor. To eliminate this source of trouble, I have designed an improved form of terminal having a water or moisture shield. Fig. 8 shows the terminal with the su porting-plate in the form which it assumes Before being bent to conform to the coil. Figs. 9 and 11 show the plate 40, which is of pliable metal, bent to closely engage about a coil. Fig. 9 shows one end 18 of the wire of the coil soldered to plate 40 in the usual way. As shown in Fig. 11, the plate 40 bears against micanite-sheet 20, (heretofore mentioned,) being bound securely in place by asbestos wrappings 25 26 of Fig. 1, passing over extensions 41 42. tubular socket 50 is cast on plate 40 and receives the stem 60 of a binding-post 61, having a flange 62, which prevents water from entering the socket. The inner end of the IIE , down about the sleeve to the Two semicircu ar thin .brass.

- now placed over the first asbestosjjacket about sleeve 51 and ti htly soldered together and to the brass ban or ring 56 along their irmer semicircular edges, care being ta en to force-the brass shield tightly down upon the first jacket. The second jacket .55 is then applied over the brass shield, so asato fit closely a out the parts of the terminal. Should water get past the outside jacket of the shield, the latter will deflect it onto the outer surface of the inner jacket away from the terminal, where it can do no damage.

Instead of forming the two jackets by'building them u on the coil itself, they may be built u on orms and applied to the coil in sectional orm. Such a method is illustrated in Figs. 12 to 15. Upona form 70, Fi 12, of a propriate dimensions, approximate y those 0 the uncovered coil, I form-a complete envelop or shell, preferabl of a thickness of about four one-hundre ths of an inch, by building up blanks of asbestos paper moistened with suitable paste in. substantially the manner described with reference to Figs 2, 3, and 4. The lap-joints between the pieces of pa er are referably hammered down with we ding e ect, and thereby reduced to approximately the thickness of the jacket where there are no 'oints. After being allowed to dry thoroug y on the form the coverin is detached by cuttin around the outer an inner edges along the lines 71 and 72 and across the sides along lines 73 and 74, thereby separating the jacket into four trough-like sections 7 5', 76, 77, and 78, adapted to fit together about the wire and lap at their ed es to form lap-joints. After scarfin the e ges of the four trough-like sections own to a bevel, so that when lapped they will not give objectionable thickness, I dampen the sections and place them to ether over the. coil in the manner shown in ig. 13. O enings for the terminalsiare of course cut t rough the sections at appropriate positions. The overlapping edges of the sections are cemented to ether with a aste, such as before mentione and the she I allowed to thoroughly dry. The coil is then immersed in a non-oxidizable waterproofing comsition, suchas parafiin composition, wit thoroughly saturated. After removal and dryin of the coil the exterior surface ma be coate with one or more-applications o the which the shell becomes same waterproofing com osition spread on .and 93, constituting the second jacket, are

constructed in substantially the same manner as the sections of the first jacket, except that the form used is slightl larger than that used for the first jacket, an the four sections are divided along different lines, so that the outer jacket will break joints with the inner jacket, as shown in Figs. 13 and 14. After the moisture in the second jacket has been allowed to thoroughly dry out the coil is im* mersed in a hot bath of baking-enamel,japan, or other drying oil or varnish. (V armshes with a linseed-oil base have been found suit able for ,the p ose.) 'When thoroughly saturated, the c dil is removed from the hot bath and is then wrap ed with a covering of asbestos tape or braid: which forms part of the outer jacket, preferably in the manner heretofore described, to form a tough protective covering. The coil can then be redipped in the hot enamel-bath until the asbestostape is thoroughl impregnated and rendered waterproof. T e resultin coil-insulation will possess high heat-resisting properties, cannot be charred by temperatures developed in electric motors, which would injure or destro the'usual insulation inwhich cotton or linen abrics are used, and is tough, durable, and waterproof.

An important characteristic of the improved insulation, which, it will be noted, is common to insulation resulting from both of of the described methods, is the em loyment of two jackets, preferabl essentia lyof asbestos,'the inner jacket eing lmpregnated with a waterproofing compound, such as those of the paraflin variety, incapable of in any way chemically reacting u on the cop per to produce compounds whic destroy or tend to destroy the insulation-between the convolutions or la ers of wire composing the coil proper, and t e second. jacket being impregnated ortreated with a high-heat-resistmg waterproofing compositionsuch as an oil-base enamel, drying-oil, or japan-which sets to a tough horny structure and which could not safel be employed in Waterproofin the first jac et.

nstead of employing asbestos ,in sheet form it may be applied in the form of plastic composition which will set when dry.

The invention may also be applied (in sub- I stantially the manner herein escribed with reference to field-coils) in insulatin armature coils or sections thereof, as we l-as to other forms of electromagnetic coils.

It will of course be understood that the process and the resulting insulation may be varied within wide limits while still employing essential and distinctive features of the invention defined in the claims which comprisin inner and 'outer jackets oflnoncom ustib e insulating material, the material of the inner jacket bein fibrous and water and moisture proofed with a non-oxidizable substance and the outer jacket being of asbestos.

2. The combination with an electromagnetic coil, of an insulating-covering therefor comprising an inner jacket of asbestos rendered water and moisture proof with a nonoxidizable substance, and an outer jacket of asbestos.

3. The combination with an electromag netic coil, of an insulating-covering therefor comprising an inner jacket of asbestos rendered Water and moisture proof with a araffin substance, and an outer jacket of as estos.

4. The combination with an electromagnetic coil, of an insulating-covering therefor comprising an innerjacket of insulating material rendered water and moisture proof with a non-oxidizable substance, and an outer jacket of insulating material rendered water and moisture proof with a high heatresisting substance.

5. The combination with an electromag netic coil, of an insulating-covering therefor comprising an inner jacket of insulatingmaterial rendered water or moisture proof with a non-oxidizable substance, and an outer jacket of asbestos rendered water and moisture proof with a high heat-resisting substance.

6. The combination with an electromagnetic coil, of an insulating-covering therefor comprising an inner jacket of insulating material. rendered water or moisture proof with a non-oxidizable substance, and .an outer jacket of asbestos rendered water and moisture proof with a drying oil or composition thereof.

7. The combination with an electromag' netic coil, of an insulating-covering therefor comprising an inner jacket of asbestos rentiered water and moisture proof with a nonoxidizable substance, and an outer jacket of asbestos rendered water and moisture proof with ahigh heat-resisting substance.

8. The combination with an electromagnetic coil, of an insulating-covering therefor comprising an inner jacket of asbestos rendered water and moisture proof with a araflin substance, and an outer jacket of as esjacket, the

tos rendered water and moisture roof with a oil or composition thereo A 9. he combination with an electromagnetic coil, of an insulating-covering or casing therefor comprising lan inner jacket of asbestos rendered water and moisture proofwith a non-oxidizable substance, an outer jacket. of

asbestos over the first jacket, and an outer wra ping of asbestos tape forming part of sai outer jacket, said ta e being rendered water and moisture proo by impregnation with a high heat-resisting substance.

10. The combination with an electromagnetic-coil,.of an insulating cove or casing therefor comprising an. inner jac ct of asbestos rendered water and moisture proof by impre tion with a paraffin composltion, an outer acket of asbestos, and a wra ping of asbestos tape forming part of said outer atter being water and moisture proofed by impregnation with a drying oil or composition thereof.

11; The combination with an electromagnetic coil, of a terminal therefor comprising a plate by which the terminal is secured in place, a conducting-shank projecting from said plate, an inner insulating-jacket extendin over the plate about the shank, a watershield about the stem and over said jacket, and an outer insulating-jacket extending over said water-shield and about the shank.

12. The combination with an electromagnetic coil, of a terminal therefor comprising a plate by which the terminal is secured in place, a conducting-shank projecting from said plate, an inner insulatingjacket extendin over said plate about the shank, a ring or and fitting tightly around the shank, a sheet or plate fitting closely around the stem and secured along its inner edge to the ring or band to constitute a water-shield, and an outer insulating-jacket over said watershield and fitting closely about the stem. I

13. The herein-described process of insulating electromagnetic coils consisting in ap' plying thereover an inner jacket of fibrous insulating material, then water and moisture proofing said jacket by impregnation with a nonoxidizable substance, app ying an outer jacket of fibrous insulating material, and then renderin said outer jacket water and moisture proo by impregnation with a high heat-resisting substance.

14. The hereindescribed process of insulating electromagnetic coils consisting in applying thereover'an inner jacket of asbestos, then water and moisture proofing said jacket by impregnation with a non-oxidizable substance, applying an outer jacket of asbestos, and then water and moisture proofing said outer jacket by impregnation with a high heatsresisting substance.

15. The'herein-described process of insulating electromagnetic coils consisting in applying thereover an inner jacket of asbestos,

then water and moisture proofing said is et gspeeification in the presence of two subsoribby iinpregnation with algamtgm cgmpo tiOIIi ing witnesses. a p 11g an outer ac et 0 as estos, an I t en water and moi ture proofing said outer LOUIS D 5 jacket by impregnation with a drying oil or Witnesses:

composition thereof; REEVE LEWIS,

In testimony whereof I have signed this WILLARD S. SUSSAN. 

